1. Field of the Invention
This invention relates to a radiation image read-out apparatus for use in a radiation image recording and reproducing system. This invention particularly relates to a radiation image read-out apparatus wherein a read-out section and an erasing section are combined integrally.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet or simply as a sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to an electric image signal, and the radiation image of the object is reproduced as a visible image by use of the image signal on a recording material such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store a radiation image until the sheet is scanned with stimulating rays to read out the radiation image. Therefore, after the radiation image is read out from the stimulable phosphor sheet, radiation energy remaining thereon should be erased to reuse the sheet.
For satisfying this requirement, it has been proposed to provide a radiation image read-out apparatus with a read-out section for reading out an image stored on a stimulable phosphor sheet, and an erasing section for erasing radiation energy remaining on the sheet.
In the proposed radiation image read-out apparatus, a cassette housing a stimulable phosphor sheet carrying a radiation image stored thereon by use of an external image recording apparatus is fed to a cassette holding section, and the stimulable phosphor sheet is taken out of the cassette and sent to the read-out section for reading out the radiation image. After the image read-out is finished, the sheet is sent to the erasing section where radiation energy remaining on the sheet is erased. The erased sheet is taken out of the read-out apparatus and reused for image recording. In general, a plurality of the erased reusable sheets are stacked in a stacking tray inside of the read-out apparatus, and taken out of the read-out apparatus in the form housed in the stacking tray. Since the sheets stacked in the stacking tray should be housed one by one in a cassette as mentioned above when they are to be reused for image recording, it is necessary to load the sheets one by one into a cassette prior to image recording. Therefore, a long time is taken for housing each sheet ready for image recording to a cassette and conducting image recording on the sheet, and it is not always possible to efficiently circulate and reuse the sheet. Also, loading of the sheet into the cassette is carried out by use of a special-purpose loader or manually, but the cost of the overall system is increased when a special-purpose loader is used, and manual loading is disadvantageous from the viewpoint of sheet processing since the sheet is directly handled. The radiation image read-out apparatus may also be constituted so that the sheet is circulated therein, taken out of a cassette after image recording, subjected to image read-out and erasing, and then conveyed and housed in a cassette. However, with such a read-out apparatus, since the read-out apparatus is exclusively occupied by a single sheet until the sheet is housed in the cassette after image read-out and erasing are conducted on the sheet, processing of the next sheet cannot be started as long as processing of the preceding sheet is being conducted. Thus an unnecessarily long time is taken, and the processing capacity of the apparatus decreases markedly.